I have custom functions set on both 5D3 and 1DX so that the set button jumps to magnified view of the focused point (and the main dial [top] scrolls the amount of magnification up or down). At times - and I haven't discovered what's different between when this happens and when not - when the image is magnified, the thumb wheel does not change images. I have to return to ordinary review mode with the playback button before I can move to another image. At other times, the thumb wheel scrolls freely between images, each magnified at the corresponding area.

Am I missing something, or have I come upon some kind of firmware glitch? It does seem odd that I get the same behavior with both cameras. Of course, now that I'm exploring and trying to reproduce the behavior, neither camera is doing it. If any of you have noticed this, can you connect it with any particular setting or operating condition?

Edit: Binh Ly explains it in the fourth post. It's when an image has just been captured and the set/magnify button is pressed before any other that the thumb wheel doesn't work. Of course, that's often exactly the time that I would like to be able to quickly compare the latest shot to the one preceding...

I have custom functions set on both 5D3 and 1DX so that the set button jumps to magnified view of the focused point (and the main dial [top] scrolls the amount of magnification up or down). At times - and I haven't discovered what's different between when this happens and when not - when the image is magnified, the thumb wheel does not change images. I have to return to ordinary review mode with the playback button before I can move to another image. At other times, the thumb wheel scrolls freely between images, each magnified at the corresponding area.

Am I missing something, or have I come upon some kind of firmware glitch? It does seem odd that I get the same behavior with both cameras. Of course, now that I'm exploring and trying to reproduce the behavior, neither camera is doing it. If any of you have noticed this, can you connect it with any particular setting or operating condition?